Mucociliary transport in living tissue: The two-layer model confirmed in the mussel Mytilus edulis L.

The present study combined video confocal laser-microscopy (1) and tissue reflectance and autofluorescence to visualize mucus position and mucociliary transport in excised living gill tissue from the blue mussel Mytilus edulis. Rafts of mucus and embedded particles were transported atop a periciliary space traversed by frontal cilia, which engaged the mucus layer and moved it during the effective stroke, disengaging and completing the cycle during the recovery stroke. These results confirm the two-layer model for mucociliary transport in the mussel gill. Given the conservative nature of ciliated epithelial structure and function (2, 3), and the structural similarity of mucociliary surfaces as diverse as terrestrial vertebrate respiratory epithelium and molluscan gill, the two-latter mechanism of mucociliary transport may be a general feature of Metazoan biology.